In connection with wind turbines it is normal practice to have a winch or hoist placed in the nacelle, for example placed in an upper position and possibly in such a manner that it can be displaced in the longitudinal direction of the nacelle and possibly also laterally. By means of such a winch or hoist various items such as tools, service parts, spare parts etc. may be lifted from the ground or sea surface up into the nacelle, for example through an opening in the floor or the side of the nacelle. Similarly, such a winch or hoist may also be used for lowering items down from the nacelle.
Such winches or hoists are equipped with a hoisting line in the form of a steel wire or a chain, which has the necessary proportions, e.g. diameter, for it to be able to handle the necessary weight, i.e. not only the weight of the item that is being lifted or lowered, but also the weight of the line that is hanging from the winch and down to the ground.
The problem of providing a hoisting line, e.g. a chain or a steel wire, with a sufficient strength has been enhanced by the fact that wind turbines have become increasingly higher in recent years, e.g. 100 to 150 meters, and they will in the next 5-6 years reach heights of 250 m. Thus, the line strength has to be correspondingly higher, meaning that the line has to be correspondingly thicker, since the line has to carry its own weight.
Thus, such winches or hoists tend to be heavy and voluminous, not only because they have to accommodate a considerable length of e.g. steel wire, but also because steel wire has a relatively large weight, whereby the reel has to be designed for handling such a relatively large weight, thereby also adding to the complexity and weight of the reel and the hoist in general. All in all, when using prior art hoists or winches equipped with steel wire in connection with e.g. wind turbines, a relatively large, heavy and complex hoisting structure has to be used, since the hoist in general has to be designed in order to cope with the relatively large weight. This gives rise to problems as regards for example the available space, for example when the nacelle of a wind turbine is concerned, where evidently a hoist can not be allowed to take up more space than absolutely necessary.
Thus, it is an object of the present invention to provide an improved hoisting device, in particular for use at a wind turbine.